Human heart valves comprise leaflets or cusps which open and close to control the flow of blood to a particular region of the heart. For example, a mitral valve includes a posterior cusp and an anterior cusp, both of which are joined at their bases to a mitral valve annulus of the heart. The mitral valve is open during diastole and closed during systole.
When the mitral valve opens, its annulus dilates or distends, along the base of the posterior cusp and when the mitral valve closes, the mitral valve annulus contracts along the base of the posterior cusp to allow the cusps to come into apposition or sealing contact with each other. In some patients with diseased heart valves, the dilation of the annulus can become permanent, and the mitral valve annulus becomes distorted during systole. The permanent dilation of the annulus causes regurgitation, i.e. backflow of blood through the valve.
These conditions as well as certain others can be addressed by implanting a support in the heart along the valve annulus. A support of this type may be rigid as described in Carpentier U.S. Pat. No. 3,656,185 or flexible as described in Carpentier et al U.S. Pat. No. 4,055,861. The rigid support, although satisfactory for some applications, does not allow the valve annulus to contract along the base of the posterior cusp and accordingly, significant stress may be imposed on the sutures, and the valve may not operate in a completely natural way. The completely flexible support, although better able to conform to dynamic changes in shape of the annulus is less effective in restoring a physiologic shape of the annulus and preventing undesired distortion. Consequently, neither the rigid support nor the flexible support allow the valve to operate in a completely natural way.